二维天线的冲激响应

本文从夫累涅尔-基尔霍夫标量衍射场方程出发,导出了并馈和串馈矩形天线在口径分布可分离时的冲激响应,以及并馈和中心串馈圆形天线在口径分布圆对称时的冲激响应它们都可以用口径幅度分布表达出来。     

Impulse responses of aperture antennas with arbitrary aperture distributions

On the basis of the equation of the Fresnel-Kirchhoff scalar diffraction field, it is shown that the impulse responses of parallel-fed aperture antennas of arbitrary configuration with arbitrary aperture amplitude distributions and those of end-fed rectangular aperture antennas with arbitrary aperture amplitude distributions can all be expressed by the aperture amplitude distributions, and that the impulse responses of rectangular aperture antennas with separable aperture distributions and those of circular aperture antennas with circularly symmetric distributions are special cases of the above general ones.     

口径天线在任意口径分布时的冲激响应

本文从夫累涅尔-基尔霍夫标量衍射场方程出发,证明了任意形状的并馈口径天线在任意口径幅度分布时的冲激响应和端馈矩形口径天线在任意口径幅度分布时的冲激响应都可以用口径幅度分布表达出来;而矩形口径天线在口径分布可分离时的冲激响应和圆形口径天线在口径分布圆对称时的冲激响应则为上述一般情况的特例。     

Prompt aperture efficiencies of impulse radiating antennas witharrays as an application

A concept of prompt aperture efficiency is introduced for the purpose of comparing and optimizing the performance of impulse radiating antennas (IRAs). The aperture efficiencies of popular lens and reflector IRAs are computed as the ratios of peak radiated power densities on boresight compared with that produced by an ideal IRA with an aperture of equal area and equal total input power. Loss of aperture efficiency occurs through two distinct mechanisms: from power that falls outside the aperture and is lost and from nonuniform power and polarization distributions within the aperture. Both loss mechanisms are addressed, and means for increasing efficiencies are identified. The optimum aperture for a given feed structure is derived. Prompt aperture efficiencies approaching 100% are feasible in TEM-horn arrays and similar structures     

Effects of a dielectric coating on leaky-wave long-slot waveguideantennas

A theoretical and experimental study is made of the effects of a dielectric of arbitrary thickness, permittivity, and loss tangent upon the aperture field distributions and the far-field radiation pattern characteristics of long-slot leaky-wave antennas cut on the broadwall of a rectangular waveguide and mounted in an infinite ground plane. The relevant integral equations for determining the aperture fields are developed and then solved using the moment method. Expressions for the far-field radiation patterns and isolation responses are developed. Calculated and experimental results for several antennas are presented and discussed     

Gaussian field expansions for large aperture antennas

An approximate theory of large aperture antennas is developed where aperture, Fresnel, and far fields are expressed in the form of Ganssian field expansions. First, aperture fields, i.e., aperture distributions, are expanded in orthogonal Hermite-Ganssian and Laguerre-Gaussian functions for antennas with rectangular and circular geometries, respectively. Then solution of the Fresnel-Kirchoff diffraction integrals yields the Fresnel and far field expansions. Care is taken to assure the direct transformability of the aperture fields. Optimal scale factors contained in the aperture field expansions are derived and lead to structured field distributions where sidelobes are added sequentially as more terms in the expansions are used in the computations. Tables of optimal scale factors and series coefficients are provided for cosine, truncated Ganssian and Taylor aperture distributions. Several examples are provided that demonstrate the usefulness of the formulas.     

Use of isorefractive media to improve prompt aperture efficiency ina lens IRA

The concept of prompt aperture efficiency is introduced for impulse radiating antennas (IRA's) and the efficiency is analyzed in detail for a specific class of lens IRA's. By using two isorefractive media, one with a low impedance within the aperture of the IRA and one with a high impedance outside the aperture, the power on the TEM transmission line-feed structure of the IRA can be concentrated within the aperture, thereby improving the prompt aperture efficiency beyond what is possible using a single medium     

A spatiotemporal representation of the electromagnetic field radiated by short-pulse superwideband antennas

It is shown that two approaches can efficiently be applied to calculate impulse responses of antennas radiating superwideband signals. The simultaneous use of these approaches makes it possible to lucidly describe the operation of certain antennas and substantially simplify the calculations. The impulse responses of some short-video-pulse scanning array antennas and the shapes of radiated signals are calculated.     

口径天线在远场区的冲激响应的含义和适用范围——兼评“也谈口径天线辐射场的瞬态特性”

本文阐明了在使用口径天线在远场区的冲激响应的概念时,远场区是对激励天线的实际信号而言,并非对为求冲激响应而施加在天线上的δ函数而言;远场区的冲激响应在距离上的适用范围决定于激励信号的频率范围。     

A transform technique for computing the radiation pattern of prime-focal and Cassegrainian reflector antennas

An efficient numerical method based on the use of the fast Fourier transform (FFT) algorithm is developed for computing radiation patterns of aperture antennas with given aperture distributions. The method is also readily applicable to the problem of computing the radiation pattern of paraboloidal reflector antennas when the induced surface currents on the surface of the reflector are known. Using an efficient launching and scanning scheme for subreflector analysis, the method is extended to a Cassegrainian reflector antenna system.     

Analytical form of EM fields radiated by circular aperture antennas of various current distributions

~~Analytical form of EM fields radiated by circular aperture antennas of various current distributions[1] Schelkunoff S. A., Advanced Antenna Theory, John Wiley &Sons, 1952. [2] E|liott R.S., Antenna Theory and Design, Prentice-Hall, Engie-wood Cliffs, N J, 1981. [3] R.W.P. King and G.S. Smith, Antennas in Matter: fundamen-tals, Theory and Applications, MIT Press, Cambirdge, MA,1981. [4] W.L. Stutzman and G.A. Thiele, Antenna Theory and Desigrn,John Wiley & S…     

Optimum aperture distributions in the presence of blockage

A method is presented for optimising the performance indices of aperture antennas in the presence of blockage. An N-dimensional objective function is formed for maximising the directivity factor of a circular aperture with blockage under sidelobe-level constraints, and is minimised using the simplex search method. Optimum aperture distributions are computed for a circular aperture with blockage of circular geometry that gives the maximum directivity factor under sidelobe-level constraints.     

Fast synthesis of aperture distributions for contoured beam reflector antennas

The use of a gradient function method to optimise aperture fields for contoured beam reflector antennas is shown to be efficient when compared with other approaches. A key feature of the method is that an analytical expression is used to modify the aperture distributions in each iteration.<>     

New technique for efficient pattern computation of aperture and reflector antennas

A new and efficient technique for computing secondary patterns of antennas with known aperture distributions is described. The method is extendable to parabolic reflector antennas with given surface current distribution. The fast Fourier transform (f.f.t.) algorithm is used to compute the coefficients of expansion of a series representing the radiation pattern.     

Realisability of uniform aperture distributions

Physical realisability of uniform aperture distributions in planar-aperture antennas has been discussed in the light of Rhodes' interpretation of the volume integrals in the complex Poynting theorem.     

低耗低剖面单层波导阵列天线研究

新型单层波导阵列天线具有低耗、低剖面、结构紧凑、实用性强等诸多优点, 在毫米波甚至太赫兹无线通信领域具有巨大应用潜力, 是当前的研究热点。 文章首先介绍了用于构建波导阵列天线的几类波导馈电网络的特点, 指出E 面波导馈电网络在毫米波应用领域的优势,接着针对E 面波导在单层并馈波导阵列天线和Butler矩阵多波束阵列天线方面的研究展开叙述,最后给出了可应用在单层波导阵列天线中的开口波导辐射单元在实现多频和圆极化等不同功能上的最新研究进展。 文章对于低耗低剖面单层波导阵列天线的发展及其应用具有参考价值。     

A new aperture coupled microstrip slot antenna

A new aperture coupled design is proposed for microstrip slot antennas to improve their radiation performance. The proposed design is based on a new aperture coupling technique in which the slot is fed by a microstrip line and coupled to several parasitic patch radiators etched on the opposite side from the slot. In contrast to the combination of a slot and a microstrip patch in conventional aperture coupled microstrip antennas, the patches here are employed to reduce the radiation into the half-space that they occupy and increase the radiation in the other half-space. Therefore, the slot antenna can produce radiation patterns with a high front-back ratio. The above objective is achieved by optimizing standing wave distributions of the aperture electric field in the slot through the adjustment of the position of the patches along the axis of the slot. In this paper, design considerations are given, and the results are validated by numerical simulations and experimental measurements.     

Approximate calculation of time-domain effective height for aperture antennas

The time-domain (TD) effective height is a space-time vector operator recently introduced to describe the performance of ultrawide-band antennas. Since generally obtained by measurements or intensive numerical modeling, it is represented through a large set of data not very suitable to the evaluation of the whole TD link. For the particular class of aperture-radiating antennas of separable shapes, such as slot, open-ended waveguides and horns, this paper proposes a systematic TD processing of the aperture field, involving model-based deconvolution and parameter estimation, at the purpose of an efficient calculation and a more manageable representation of the effective height. Following the idea at the base of modal near to far field transformation, as previously presented by the authors, the processing of the aperture impulse response is here addressed with a particular care to the fast varying early transient. The corresponding time-dependent Radon transforms are then approximated by semi-analytical formulas whose accuracy is discussed as for the aperture size and frequency limits. The proposed methods, which are much faster than the conventional approach, are demonstrated by some examples.     

Ray tracing method for doubly curved reflector surfaces

Shaped reflector surfaces designed for microwave antennas are often defined by a regular grid of discrete points. A ray tracing procedure useful for computing aperture and power distributions produced by an arbitrarily shaped reflector surface is described.     

Characteristics of aperture coupled microstrip antennas withvarious radiating patches and coupling apertures

A full wave moment method is applied to the analysis of aperture coupled microstrip antennas, in which all components of the electric and equivalent magnetic surface currents are considered. The electric current distributions on the rectangular patch for different coupling aperture positions are presented with their radiation patterns. The effects of the coupling aperture shape and size on the input impedance and radiation performance are also discussed. As an example of new radiators, slotted patches are studied, and it is shown that they can be used to achieve dual-frequency operation